Inactive modifications

Active modifications

Melting point


37 to 38°


112 to 113°

107 „ 108°


159 „ 160°

151 „ 152°

Methoethyl heptanonolid


46 „ 47°

a-Terpineol is a tertiary, unsaturated alcohol which yields addition products with bromine, nitrous acid anhydride, nitrogen-tetroxyde and nitrosylchloride. The nitrosochloride and the nitro-lamine bases derived therefrom are especially adapted for the characterization of the a-terpineol (see p. 380).

The liquid dibromide yields a tribromide when treated with hydrogen bromide in glacial acetic acid solution. Further treatment with bromine converts it into dipentene tetrabromide melting at 124°.

With hydrohalogen acids the corresponding dipentene di-halogen hydrides result. The dihydriodide C10H18I2 (m. p. 77 to 78°), obtained by shaking the alcohol with concentrated hydriodic acid, can be utilized for the identification of terpineol.1) Toward mineral acids and also toward some organic acids, terpineol is rather unstable. Whereas shaking with dilute sulphuric acid hydrates it to terpinhydrate,2) boiling therewith causes it to be dehydrated with the formation of terpinene together with a little dipentene and cineol. Potassium acid sulphate has a similar effect producing principally dipentene; also phosphoric acid producing principally terpinolene with small amounts of terpinene and cineol; also oxalic acid which likewise produces terpinolene.8) Acetic acid anhydride also dehydrates terpineol, especially when heated, producing dipentene. Hence it is not possible to esterify terpineol quantitatively with this agent without exercising special precautions.1) For further details concerning terpinylacetate see the chapter on esters.

1) Wallach, Liebig's Annalen 230 (1885), 265.

2) Tiemann and Schmidt, Berl. Berichte 28 (1895), 1781.

3) Wallach, Liebig's Annalen 275 (1893), 104; Baeyer, Berl. Berichte 27 (1894), 447.

When oxidized with dilute permanganate solution, terpineol is first converted into the polyatomic alcohol C10H20O3, 1,2,8-tri-hydroxymenthane (m. p. of the inactive modification 122°). Chromic acid mixture oxidizes this to a ketolactone C10H16O3 (m. p. of the active modification 46 to 47°, of the inactive 64°). The study of this compound has contributed much toward the establishment of the constitution of terpineol as expressed by the formula v1 -terpene-8-o1. More violent oxidation of the terpineol and of the ketolactone with chromic acid mixture or nitric acid yields terpenyl and terebinic acids.2)

Of special interest is the conversion of terpineol, through the tribromide and the nitrosochloride, into derivatives of carvone.3)

The hydroxy group of terpineol reacts with phenylisocyanate when both compounds are mixed and set aside at room temperature for a time. Sometimes crystals of diphenylurea separate at first, from which the liquid mixture is separated with the aid of cold anhydrous ether or, better still, with low boiling petroleum ether. After careful evaporation of the solvent, the urethane separates in fine needles. Recrystallized from alcohol, the inactive compound melts at 113V) The urethane obtained from optically active terpineol is likewise inactive. The a-naphthyl-urethane,5) melting at 147 to 148° can also be utilized for the identification of a-terpineol. Especially suited to this purpose is the nitrosochloride.

According to Wallach6) the preparation of the nitrosochloride is accomplished in the following manner: To a solution of 15 g. terpineol in 15 ccm. glacial acetic acid and 11 ccm. ethylnitrite, well cooled in a freezing mixture and while well shaken, 6 ccm. of hydrochloric acid dissolved in an equal volume of glacial acetic acid, are added drop by drop. At the close of the reaction the nitrosochloride is precipitated with ice water in the form of an oil which, however, soon crystallizes. The solid compound is purified by recrystallization from hot acetic ether or methyl alcohol and melts at 112 to 113°. The active modification melts at 107 to 108°.

12) Ginsberg, Journ. russ. phys. chem. Ges. 29 (1897), 249. According to Chem. Zentralbl. 1897, II. 417; Report of Schimmel & Co. October 1897, 63. Compare also the chapter "Examination of volatile oils" under acetylation.

2) Wallach, Liebig's Annalen 227 (1893), 117, 120; 291 (1896), 345; Berl. Berichte 28 (1895), 1775; Tiemann and Mahla, Berl. Berichte 29 (1896), 928; Tiemann, ibidem 2616.

3) Wallach, Liebig's Annalen 281 (1894), 140; 291 (1896), 346.

4) Wallach, Liebig's Annalen 275 (1893), 104.

5) Report of Schimmel & Co. October 1906, 41.

6) Liebig's Annalen 277 (1893), 120; 360 (1908), 90.

With piperidine in alcoholic solution, the nitrosochloride yields the nitrolpiperidine base C10H17(OH)NONC5H10, which is difficultly soluble in ether, crystallizes from methyl alcohol in needles that melt at 159 to 160°. These data by Wallach refer to the derivative obtained from an optically inactive terpineol. The nitrol piperidide obtained from an optically active material melts several degrees lower, namely at 151 to 152V)

With aniline a terpineol nitrolanilide, m. p. 155 to 156°, is obtained.